Which genetic transfer mechanism does not require cell-to-cell contact?

Transformation is the genetic transfer mechanism that does not require cell-to-cell contact. In this process, competent bacterial cells take up free DNA from their environment. This DNA may come from lysed bacteria or other sources and can be incorporated into the recipient's genome through homologous recombination.

This method allows for horizontal gene transfer, impacting genetic diversity without the direct involvement of living cells in close proximity to each other. Unlike conjugation, which necessitates cell-to-cell contact through a pilus, and transduction, which requires a bacteriophage to mediate the transfer of DNA, transformation occurs freely in the surrounding environment. Binary fission, on the other hand, is an asexual reproduction method and does not involve any form of gene transfer; it simply replicates the genetic material of a single cell to produce two identical daughter cells.

Thus, transformation stands out as the unique mechanism of genetic transfer that operates independently of physical contact between cells.